Home NodeB (HNB), Home eNB (HeNB) and femto cell are concepts introduced for UMTS and LTE (E-UTRAN) to improve indoor and micro-cell coverage as well as to leverage wireline backhaul to the ‘home’. “Femto” cell is widely used outside of 3GPP to mean any cell with a very small coverage, and typically installed in a private premises (either private or corporate or residential/enterprise). The Home NodeB (HNB), Home eNB (HeNB) and femto cell can have a residential or enterprise IP network. The terms HeNB/HNB are used in 3GPP with specific meanings i.e. that the cell is a closed subscriber group (CSG). A CSG identifies subscribers of an operator who are permitted to access one or more cells of the public land mobile network (PLMN) but which have restricted access. A H(e)NB subsystem supports Local IP Access in order to provide access for IP capable UEs connected via a H(e)NB subsystem (i.e. using H(e)NB radio access) to other IP capable entities in the same residential IP network or enterprise IP network.
The term “macro” cell, while not having significance in 3GPP specifications, is widely used to mean a cell other than a CSG cell.
An important aspect of HeNB/HNB functionality is the ability to restrict access to particular users. For example, to employees of the company on whose site the HeNB is deployed, to customers of a particular coffee shop chain, or (in the case of HeNBs deployed in private homes) to individuals.
To achieve this functionality, 3GPP has defined the concept of the CSG. The CSG cell is one which indicates that it is a CSG cell (by means of 1 bit broadcast in the system information) and broadcasts a CSG ID (also in system information). A cell can only indicate one (or none) CSG IDs, however multiple cells may share a CSG ID. A user equipment (UE) device may be subscribed to multiple CSGs. The UE may for example may be a mobile terminal such as, but not limited to a cellular telephone, a personal data assistant (PDA), or a wirelessly enabled computer. A subscription may be temporary in nature (e.g. a coffee shop allows a customer one hour's access to its CSG).
3GPP is also introducing the concept of selective IP traffic offloading, for which an introduction is provided below.
Local IP Access (LIPA) allows an IP-capable UE connected via a femto cell direct access to other IP-capable devices in the local residential/corporate IP network.
Selected IP Traffic Offload (SIPTO) is used to offload selected types of IP traffic (e.g. internet traffic) towards a defined IP network close to the UE's point of attachment to the access network. SIPTO is applicable to traffic offload for the macro-cellular access network and for the femto cell subsystem.
LIPA PDN Connectivity indicates a PDP Context (in the case of a GERAN or UTRAN femto cell connected to a GPRS core network) or a PDN Connection (in the case of an E-UTRAN femto cell connected to a GPRS core network) that gives access to services located in the local residential/corporate IP network of the femto cell subsystem.
SIPTO PDN Connectivity indicates a PDP Context or PDN Connection that allows offload of selected types of IP traffic (e.g. internet traffic) towards a defined IP network close to the UE's point of attachment to the access network. SIPTO is applicable to traffic offload for the macro-cellular access network and for the femto cell subsystem.
Remote PDN Connectivity indicates a regular PDP Context or PDN Connection established neither according to LIPA PDN Connectivity nor SIPTO PDN Connectivity.